Phylum: Nemathelminthes Nematoda Ascaris By Assist. lecturer Maytham A. Alwan Nematoda :introduction Nematodes Appearance and Morphology 1. Variable length, 1 mm to several meters. 2. Most nematodes have a cylindrical form, tapering at either end, and the body is covered by a colourless, somewhat translucent(the cuticle which may form specialized structures (e.g., alae). • The cuticle is secreted by the underlying hypodermis, which projects into the body cavity forming two lateral cords, which carry the excretory canals, and a dorsal and ventral cord carrying the nerves .The muscle cells, arranged longitudinally, lie between the hypodermis and the body cavity. Characteristics of the Nematoda 4/13/2015 3 Nematoda:Structure and function 3. Usually sexually dimorphic (separated sex) with males smaller than females. 4. The body is bilateral symmetry. 5. Most of the internal organs are filamentous and suspended in the fluidfilled body cavity. A. The digestive system is tubular. The mouth of many nematodes is a simple opening which may be Surrounded by two or three lips, and leads directly into the oesophagus. In others, such as the strongyloids, it is large, and opens into a buccal capsule, which may contain teeth. 4/13/2015 4 Morphology B. The reproductive systems consist of filamentous tubes. The female organs comprise ovary, oviduct and Spicules uterus, which may be paired, ending in a common short vagina which opens at the vulva. • The male organs consist of a single continuous testis and a vas deferens terminating in an ejaculatory duct into the cloaca. 4/13/2015 5 Characteristics of the Nematoda Digestive system Assist lec. Maytham Al-Shabbani Nervous system 4/13/2015 7 Excretory system 4/13/2015 8 Characteristics of the Phylum Nematoda Reproductive system consists of tubular organs lying in the pseudocoelom. MALE nematodes are generally smaller in size. Assist lec. Maytham Al-Shabbani Characteristics of the Phylum Nematoda FEMALE nematodes are larger in size. The female reproductive organs are doubled. Assist lec. Maytham Al-Shabbani Ascaris Kingdom: Animalia Phylum: Nemathelminthes Class: Nematoda Order: Ascaroidea Family: Ascarididae Genus: Ascaris Species: A. lumbricoides (human), A. suum (pigs) 4/13/2015 11 Morphology • Adult: The adults are cylindrical in shape, creamywhite or pinkish in color. The female averages 20-35cm in length, the largest 49cm. The male is smaller, averaging 15-31cm in length and distinctly more slender than the female. The typical curled tail with a pair sickle like copulatory spines. On the tip of the head there are three lips, arranged as a Chinese word “ 品 ”. They have a complete digestive tract. Reproductive organs are tubular. male has a single reproductive tubule. The female has two reproductive tubules and the vulva is ventrally located at the posterior part of the anterior 1/3 of the body. Assist lec. Maytham Al-Shabbani Adult worm of A. lumbricoides Assist lec. Maytham Al-Shabbani The lips of Ascaris lumbricoides The three lips are seen at the anterior end. The margin of each lip is lined with minute teeth which are not visible at this magnification. Assist lec. Maytham Al-Shabbani 4/13/2015 Assist lec. Maytham Al-Shabbani 15 • Egg: There are three kinds of the eggs. They are fertilized eggs, unfertilized eggs and decorticated eggs. We usually describe an egg in 5 aspects: size, color, shape, shell and content. Assist lec. Maytham Al-Shabbani • Egg: There are three kinds of the eggs. They are fertilized eggs, unfertilized eggs and decorticated eggs. We usually describe an egg in 5 aspects: size, color, shape, shell and content. Semilunar space Vitelline layer (1st) One cell stage 2nd layer (thick) 3rd layer outer coarse albuminous layer (regular) Fig . : Ascaris lumbricoides- Egg Fig . : life cycle of Ascaris lumbricoides Assist lec. Maytham Al-Shabbani